More specifically, the present invention employs a unit for forming groups of products, the unit being of the type comprising a production machine for producing the products; a group-forming machine for forming the products into groups of K products; and a transfer assembly for transferring the products from the production machine to the group-forming machine; the transfer assembly comprising a first output conveyor of the production machine, and a second input conveyor of the group-forming machine; the first and second conveyor moving respectively in a first and second direction opposite each other, and respectively comprising first and second pockets with a first and second spacing respectively.
Though suitable for any type of product, the present invention may be used to advantage in the tobacco industry, on a cellophaning-cartoning unit, to which the following description refers purely by way of example, and for packing, on a group-forming machine defined by a cartoning machine comprising an input pocket conveyor, groups of K packets of cigarettes produced on a production machine—in this case, a cellophaning machine—comprising an output pocket conveyor.
The output and input pocket conveyors of known units of the type described above used to form a single transfer pocket conveyor for transferring packets directly from the cellophaning machine to the cartoning machine in a single orderly succession.
Such a solution had the obvious advantage of maintaining precise timing of the two machines, but also the obvious disadvantage of failing to compensate for any voids, i.e. empty pockets, along the transfer conveyor, and so preventing the formation of incomplete groups on the cartoning machine.
To eliminate the above drawback, it has since been proposed to keep the output and input conveyors separate, and to connect them with the interposition of a FIFO (first-in-first-out) inter operational store, which receives a first orderly succession of packets in time with the cellophaning machine, and in which the packets are formed into queues, from which the packets are withdrawn by the input pocket conveyor of the cartoning machine and again formed into a second succession in time with the cartoning machine.
This provides for compensating for any voids along the output conveyor of the cellophaning machine, but results in a loss of synchronization of the two machines. Moreover, at relatively high production speeds, withdrawing the packets from the queues formed in the inter operational store is neither straightforward nor easy, and may easily result in damage to the packets.
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